1. Field of the Invention
The present invention relates generally to a microstrip antenna for use on a missile or the like. More specifically, the present invention relates to a microstrip antenna which includes a plurality of tuning tabs for tuning the antenna frequency of the microstrip antenna.
2. Description of the Prior Art
A microstrip antenna operates by resonating at a frequency. Conventional design techniques for a microstrip antenna use printed circuit technology to place a printed copper patch on the top of a layer of a dielectric and a ground plane on the bottom of the dielectric. The frequency that a microstrip antenna operates at is approximately a half wavelength or a quarter wavelength with one side grounded in the microstrip medium of dielectric below the copper patch and air above the copper patch. On high performance projectiles (e.g. missiles), a protective dielectric cover is used to protect the antenna from the environment.
Without a protective cover, a portion of the microstrip antenna can be removed to tune the microstrip antenna up in frequency. When there is a cover to protect the microstrip antenna, the microstrip antenna is normally tuned by using tuning slugs which are screwed in an upward direction from the ground plane of the antenna toward the microstrip antenna's copper patch. As the slug is tuned toward the microstrip antenna, there is an increase in capacitance which lowers the operating frequency of the microstrip antenna.
For low frequency operation, the usual amount of space available for the microstrip antenna dictates a very narrow frequency bandwidth.
Further, due to manufacturing tolerances, there is need for a tuning apparatus for tuning the antenna frequency which achieves an acceptable failure rate for antennas in production.